11. What turns off in your brain that allows you to accept such oddities in dreams?[/b]
What turns off (during REM sleep) are the neurotransmitters Serotonin & Noradrenaline (NE).

When we're awake, these give us our awareness & our consciousness (of ourselves), and our ability to question things & consider things critically. They also help us to lay down new memories (which is why we remember things that happen to us when we're awake much more easily than we do when we're dreaming).

That's why, if you increase your Serotonin/ NE levels @ night (by eating cheese, peanuts, banana, chocolate .. etc.. or by taking supplements like L-Tyrosine, L-Tryptophan or St John's Wort ... or even slapping on a nicotine patch ), you're much more likely to remember your dreams & also more likely to become aware that you are dreaming (become lucid).

That's kinda the theory anyway.